In a processing system where two or more processing cores or hyper-threads (HTs) exist, the operating system (OS) normally owns all of those processing units. When the workload of the processing system is low or idle, the OS may shift all of the processing units into a low power or standby mode. For instance, Revision 3.0a of the Advanced Configuration And Power Interface (ACPI) Specification, dated Dec. 30, 2005 (the “ACPI Specification”) describes standard interfaces for OS-directed configuration and power management on laptops, desktops, and servers. The ACPI Specification may be obtained from www.acpi.info/spec.htm.
However, existing processing systems do not support separate power planes for each processing core or HT. For example, when a conventional platform with two processing cores changes the sleep state of the processing system, the platform must set both of the processing cores to the same ACPI sleep state.